GGE Biplot Analysis of Genotype by Environment Interaction and Yield Stability in African Yam Bean (Sphenostylis stenocarpa)

Abstract

Aims: To identify the genotype(s) most suited for the test environments in Nigeria and to understand the nature of genotype-by-environment interaction (GEI) effects on AYB production. Study Design: Multi-environment trials combined with GGE biplot analysis to explore genetic interactions and determine the adaptability and stability of African yam bean accessions across diverse environments. Place and Duration of Study: The research was conducted over four environments, Umudike (rainforest) and Ibadan (derived savanna), during two consecutive years in 2020 (late season) and 2021 (early season). Methodology: Eighty-six AYB accessions were evaluated using a randomized complete block design with three replications. Each accession was planted in a 3-meter-long ridge, with 1meter spacing between plants within the row. Rows were spaced 15 meters apart, with 1 meter spacing between plants within rows. Two seeds were initially planted per stand, later thinned to one plant, resulting in three plants per accession. Plants were staked with bamboo sticks three weeks after plantings. NPK fertilizer (15-15-15) was applied seven weeks after planting and data were taken on vegetative and reproductive characteristics. Results: Combined analysis across environments revealed that genotypes and GEI significantly impacted AYB yield. The biplot polygon of “which-won-where” showed accessions TSs508, TSs518, TSs542, TSs544, TSs600, TSs598, TSs605, and TSs550 as winners. Accession TSs554 gave the highest yield in all test environments. Accessions TSs549, TSs555, TSs575, TSs604, and TSs563 were the most adaptable and the stable accessions were TSs591, TSs507, TSs517, and TSs 538. UMU 2021 is regarded as a superb environment in terms of discrimination and representativeness. Conclusion: These accessions are suggested as parental lines in breeding programs for increasing grain and tuber yield in derived savanna or rainforest agroecological zones of Nigeria.